A supplemental inflatable restraint system in an automotive vehicle comprises one or more supplemental inflatable restraint devices, for example a driver's side air bag and a passenger's side air bag. Each supplemental inflatable restraint device is initiated by its own independent electrical circuit, and each circuit includes an inertia switch which is devoted exclusively to the corresponding supplemental inflatable restraint device.
While suitable mounting location(s) on a vehicle's structure for such switches is (are) typically selected on the basis of a number of factors, one important consideration involves the ability of a mounting location to respond in a consistent manner to impact forces. In order to then secure consistent inertia switch performance in such a location, it becomes necessary to have consistency in the manner in which the switch mounts on the vehicle structure, and consistency in the switch construction itself. Inability to meet either or both of these criteria may give rise to installations in which an inertia switch does not respond in the manner in which it is intended. For mass-production environments, consistency and reliability are promoted by making fabrication and assembly procedures as facile as possible.
Other factors come into play as well. The mechanisms of certain inertia switches may require shielding from certain environmental influences. For one example, in an inertia switch of the type containing a magnet that holds the inertial mass in place during quiescent and normal conditions, shielding of the magnetic circuit from external magnetic forces may be required. For another example, the inertia switch may be located in an area that is exposed to dirt or contamination, and in this case proper protective enclosure of the mechanism is called for. Similarly, if the inertia switch is in a location where it could be tampered with, a tamper-proof or at least a tamper-evident housing should be used to thwart attempted tampering. Still further, the inertia switch should be capable of withstanding substantial impacts so that it can continue to provide proper functioning in the event of receiving such impacts.
The present invention relates to a new and improved mounting housing for an inertia switch that is used to signal a supplemental inflatable restraint operating circuit in a manner that avoids spurious signalling during periods of normal vehicle operation, yet will provide proper signalling at the time that such signalling is intended to occur. The invention possesses a number of novel feature which provide benefit.
One feature is that portions of the circuitry associated with the inertia switch are embodied in a portion of the inertia switch assembly itself. This eliminates the need to use a separate circuit board assembly for the mounting of the circuit components involved. Another feature is the arrangement of an internal seal in such a manner that the potential for outgassing is reduced during a potting operation that is conducted during the fabrication process, and more consistent internal element pressures are attained. A further feature is the arrangement of an internal steel keeper in such a manner that an internal magnetic circuit is suitably shielded from external influences while a more efficient internal magnetic circuit results. Such improvements in the internal magnetic circuit may permit the downsizing of certain internal components with attendant potential for economies in size, weight and cost.
The invention also contemplates improvements in the fabrication process by allowing a pre-filled potting compound to be used in place of a previously used form of potting which was more labor-intensive. Specifically, the invention enables the following operations to be eliminated: epoxy sealing of contacts; element assembly roll-over (because the element assembly is now a snap fit); element de-pressurization; circuit board assembly; soldering of circuit board connections; post-solder de-fluxing; circuit board conformal coating; manual assembly of element into housing; positioning of foam spacers in housing; glueing of elements and grommets into housing; addition of sand to potting compound; and the vibration/mixing of the sand into the potting. The reduction in the number of operations required to fabricate an inertia switch makes the process more cost-efficient. It also results in reduced variability from part to part. More accurate alignment of the element to the axis of motion makes for improved response to impact.
Further features, advantages and benefits of the invention will be seen in the ensuing descriptions and claims. Drawings accompany the disclosure and illustrate a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.